With recent rapid progress of various communication systems using an electromagnetic wave in the microwave region, such as car telephone, cellular phone and satellite broadcasting, a large number of dielectric materials have been developed. This dielectric material is demanded to simultaneously satisfy three characteristic features, that is, (1) the dielectric constant (εr) is high, (2) the coefficient of unloaded quality (Qu) is large and (3) the absolute value of temperature coefficient of resonance frequency (τf) is small.
As for the dielectric material having a relatively high dielectric constant, BaO—RE2O3—TiO2 materials (RE: rear earth element) and the like are known at present (see, JP-A-6-309926 (the term “JP-A” as used herein means an “unexamined published Japanese patent application” and JP-A-2000-7429) and being used for resonator, filter and the like.